A. Field of Invention
This invention pertains to the art of methods and apparatuses regarding spine surgery and more specifically relates to surgical procedures, associated instrumentation and a motion preserving implant to be positioned within, and in some embodiments deployed within, a vertebral space.
B. Description of the Related Art
The volume of spinal surgeries to treat degenerative disc and facet disease has steadily increased over the past decade, fueled by population demographics and advancements in diagnostic and instrumentation adjuncts. Improvements in intraoperative radiological imaging and surgical technique have generated a great deal of interest in applying minimally invasive surgical (MIS) techniques to spinal applications. As in other surgical subspecialties, it is hoped such minimally invasive techniques applied to spinal surgery will result in less soft tissue trauma, less operative blood loss, reduced operative time, faster recovery periods and lower costs.
Known spinal surgical techniques, though generally working well for their intended purposes, have been adopted from traditional open surgical (non-MIS) techniques. As a result, known spinal surgical methods, instrumentation and interbody implants have disadvantages. One disadvantage is that the physical components are relatively large and bulky. This reduces surgeon visualization of the surgical site. Another disadvantage of know spinal surgical methods is that known surgical tools and implants are cumbersome and difficult to maneuver within the limited surgical space available.
As a result of the aforementioned disadvantages, many intradiscal “fusion” implants have been developed to replace a degenerative disc and to maintain stability of the disc interspace between adjacent vertebrae until a solid arthrodesis has been achieved. These known “interbody fusion devices” have had variable geometries and have been classified by Zdeblick et al. in U.S. Pat. No. 6,695,851 into two basic categories; solid implants and bony ingrowth implants. Examples of solid implants are provided in U.S. Pat. Nos. 4,878,915, 4,743,256, 4,349,921 and 4,714,469. The previously noted patent to Zdeblick et al. (U.S. Pat. No. 6,695,851) as well as U.S. Pat. No. 4,820,305 to Harms et al. are examples of bony ingrowth implant devices. Other types of implants in the interbody fusion device category are provided in the following U.S. Pat. No. 5,397,364 to Kozak; U.S. Pat. No. 5,015,247 to Michelson, U.S. Pat. Nos. 4,878,915, 4,743,256, 4,834,757 and 5,192,327 to Brantigan; U.S. Pat. Nos. 4,961,740 and 5,055,104 to Ray; and 4,501,269 to Bagby.
The devices provided in the aforementioned references all have relatively fixed geometries, most commonly rectangular, trapezoidal, or cylindrical in shape. Jackson, in U.S. Pat. No. 6,773,460, has developed anterior interbody device that is expandable relative to the vertical axis of the intradiscal space. Despite this progression in intradiscal implant geometry, a device having an optimized geometry to provide an optimal vertebral endplate footplate is lacking. A specific surgical method and complementary implant instrumentation system is also lacking. Various surgical methods have been devised for the implantation of interbody fusion devices. Dr. Gary Michelson's technique and associated instruments as provided in U.S. Pat. No. 5,484,437 is but one example. These known techniques along with their associated instruments and implants lack one or more of the criteria for optimal use in anterior, posterior, or transforaminal minimally invasive approaches compatible with currently available minimally invasive spine surgery and/or minimal access spinal techniques (MAST).
The present invention provides methods and apparatuses for overcoming these disadvantages by providing an interbody implant, that in some embodiments provides motion-preserving articulation, that allows for minimally invasive spinal surgery.